[Bug] Sieve vacation :addresses match only case-sensitive?

[Sami Ketola]

> On 9 Sep 2019, at 16.17, Philipp Faeustlin via dovecot <dovecot at dovecot.org> wrote:
> 
>>    It is not recommended to rely on local-part case, but it is indeed
>>    case-sensitive.
>>    And this is to avoid such issues that postfix supports address
>>    cleanup/canonicalisation before forwarding mails to dovecot.
>>    ----------
>>    RFC 5321:
>>    "Local-part     = Dot-string / Quoted-string ; MAY be case-sensitive
>>    […]
>>    While the above definition for Local-part is relatively permissive,
>>    for maximum interoperability, a host that expects to receive mail
>>    SHOULD avoid defining mailboxes where the Local-part requires (or
>>    uses) the Quoted-string form or where the Local-part is case-sensitive."
>> And therefore “receive liberally” policy that wants to assume case-insensitivity should single-case the address IN THE COMPARISON.
> The local-part MAY be case-sensitive, but in general I don't know any mail addresses where the case matters.
> Thus it is hard for me to understand, why this comparison of the vacation address is case-sensitive. Whether the final recipients address is also treated case-insensitive.
> 
> If this has to be case-sensitive to be RFC compliant, then please create an option for admins or users to change the behavior to an case-insensitive comparison.
> 

Just change auth_username_format = %Lu to make all addresses lowercase. That should solve your problem.
Or if you REALLY REALLY want to have case-sensitive userpart, then use auth_username_format = %n@%Ld

Sami